The early Rotax engined ones had some serious issues, fuelling, etc., - a lot of reports at the time said the thing just wasn't properly sorted before they released it - so much so that they had to have a weird sort of 'relaunch' of the same bike which was basically a tacit admission that they'd screwed up and had now fixed it ... except a lot of the mags reckoned they still hadn't got it 100 per cent.
Add to that the fact that they're ugly as **** and I'd say a pristine S1 Lightning would be a much better investment.